1. Field of the Invention
The present invention relates to an apparatus for inflating a vehicle occupant restraint such as an air bag. More specifically, the present invention relates to an apparatus including a pressure vessel which contains gas for inflating an air bag, and an assembly for detecting leakage of the gas from the pressure vessel.
2. Description of the Prior Art
U.S. Pat. No. 3,771,121 discloses an apparatus including a pressure vessel which contains gas for inflating an air bag in a vehicle. The apparatus also includes a pressure sensing assembly which senses the gas pressure within the pressure vessel. The pressure sensing assembly includes an electrically conductive diaphragm which is supported within the pressure vessel. The pressure sensing assembly has a conducting mode in which the gas pressure within the pressure vessel holds the diaphragm in contact with an electrical contact member. The diaphragm thus completes an electrical circuit between a power source and the electrical contact member when the pressure sensing assembly is in the conducting mode. When the gas pressure within the pressure vessel falls below a predetermined level which is required to inflate the air bag, the gas pressure is no longer sufficient to hold the diaphragm in contact with the electrical contact member. The diaphragm then moves out of contact with the electrical contact member, and the pressure sensing assembly is thus shifted into a non-conducting mode. A switching assembly senses shifting of the pressure sensing assembly into the non-conducting mode, and responds by actuating a lamp on the vehicle instrument panel to indicate to a vehicle occupant that the gas pressure has fallen below the level required to inflate the air bag.